Numerical Simulation of Wave Propagation and Sediment Suspension Affected by Submerged Rigid Vegetation

Abstract:

Due to the vegetation-induced turbulence， the suspended sediment concentration in the rigid vegetated bed increased significantly， relative to the bare bed. The traditional sediment model which calculates the bed shear stress by mean velocity cannot simulate the phenomenon. Therefore， based on the physical modelling experiment of hydro-sediment dynamics in vegetated flows， a three-dimensional mathematical model of wave propagation with submerged rigid vegetation was established using Flow–3D in this paper to simulate the hydrodynamic characteristics and sediment suspension process under the influence of vegetation. Meanwhile， the original sediment model in Flow–3D was improved by modifying Shields number using turbulent kinetic energy. Compared with the experimental data， the model could accurately reproduce the decrease of mean wave velocity in the entire water column and increase at the top of the canopy， the enhanced turbulence caused by vegetation， and the two peaks of turbulent kinetic energy in the wave period. Using the improved sediment model considering the influence of vegetation wake turbulence on sediment movement， the accuracy of sediment suspension simulation in vegetated bed was significantly higher than the results from the original sediment model.